US5968050A - Positioning a tibial tunnel - Google Patents

Abstract

A guide for positioning a tibial tunnel in anterior cruciate ligament (ACL) reconstruction. The guide includes a guide arm and a drill sleeve connected to the guide arm. A distal tip of the guide arm is configured to contact a femoral surface, and a distal tip of the drill sleeve is configured to contact a tibial surface when the distal tip of the guide arm contacts the femoral surface.

Description

TECHNICAL FIELD

This invention relates to positioning a tibial tunnel in anterior cruciate ligament (ACL) reconstruction.

BACKGROUND INFORMATION

A damaged ACL is often replaced with a graft from a patellar tendon or a semitendinosus tendon. Generally, the patellar tendon graft has small bone pieces attached to its ends, whereas the semitendinosus tendon graft does not. Tunnels are formed in the tibia and femur for use in implanting the graft in the patient's knee. The graft is then secured in the tunnels by fixation means, such as, for example, interference screws or sutures tied to screw posts.

SUMMARY

This invention features a guide for positioning a tibial tunnel in anterior cruciate ligament (ACL) reconstruction.

In one general aspect of the invention, the guide includes a guide arm and a drill sleeve connected to the guide arm. A distal tip of the guide arm is configured to contact a femoral surface, and a distal tip of the drill sleeve is configured to contact a tibial surface when the distal tip of the guide arm contacts the femoral surface.

Embodiments may include one or more of the following features. For example, the guide may include a handle to which the guide arm and the drill sleeve may be connected, such that the guide arm and the drill sleeve are connected through their connections to the handle. The guide arm may be located at one end of the handle, and the drill sleeve may be located at an opposite end of the handle.

An orientation of the guide arm may be adjusted with respect to the drill sleeve. The guide arm may have markings for indicating the orientation of the guide arm with respect to the drill sleeve.

The drill sleeve may be configured to direct a guidewire into the tibial surface to locate the tibial tunnel. The drill sleeve may have markings for measuring the length of the tibial tunnel. The distal tip of the drill sleeve may include an angled opening surrounded by teeth.

The distal tip of the guide arm may include a hook configured to contact the femoral surface at, for example, the posterior cortex of the femoral notch. The guide arm may provide an offset from a point at which the distal tip contacts the femoral surface (e.g., the posterior cortex of the femoral notch) to a longitudinal axis of the drill sleeve (i.e., the axis of the tibial tunnel).

The distal tip of the guide arm also may include a spike configured to contact a tibial plateau. The size of the spike may vary depending on the desired ease of insertion of the guide arm. For example, the guide arm is easy to insert into the patient's knee when the spike is short.

In other embodiments, the guide arm may include a first distal arm portion having a hook configured to contact the femoral surface and a second distal arm portion having a spike configured to contact the tibial plateau. When the guide arm includes two distal arm portions, the guide may be adjusted to compensate for various femoral offsets and femoral notch heights.

The first distal arm portion may be configured to slide over the second distal arm portion. This permits adjustment of the guide to compensate for various femoral offsets. Alternatively, the first distal arm portion may be attached to the second distal arm portion by a spring. This permits adjustment of the guide to compensate for various femoral notch heights. In other embodiments, the first distal arm portion may be attached to the second distal arm portion by a linkage or at a pivot point. The guide arm is easy to insert into the patient's knee when the two distal arm portions are attached at a pivot point because the pivot point permits the spike to be deployed into the tibial plateau.

In other embodiments, the guide may include a device for indicating isometry. Isometry exists when the distance between the femoral tunnel opening and the tibial tunnel opening remains constant during extension of the knee. The device may be an isometry linkage. The length of the isometry linkage may be adjusted to compensate for various femoral notch heights by using hydraulic means or another extending mechanism. The device also may be an isometry mechanism located outside the patient's knee or an isometry suture.

Another general aspect of the invention features a method for positioning a tibial tunnel using the guide discussed above. In use, the guide is positioned in a patient's knee so that the distal tip of the drill sleeve contacts the tibial surface and the distal tip of the guide arm contacts a femoral surface (e.g., the posterior cortex of the femoral notch). Next, a guidewire is inserted through the drill sleeve and drilled through the tibia. The guide is removed from the patient's knee, leaving the guidewire in place to locate the tibial tunnel. Finally, a cannulated drill bit is placed over the guidewire for drilling the tibial tunnel.

Among other advantages, the invention provides an efficient and accurate way of positioning the tibial tunnel. For example, the guide references a bone surface (e.g., a femoral surface) for positioning the tibial tunnel, rather than a soft tissue surface. Moreover, the guide references a particular region of the femoral surface (e.g., the posterior cortex of the femoral notch) for positioning the tibial tunnel.

Other features and advantages of the invention will be apparent from the following detailed description, including the drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is side view of a guide for positioning a tibial tunnel.

FIG. 2A is a side view of a handle of the guide of FIG. 1.

FIG. 2B is an end view of the handle of FIG. 2A.

FIG. 3A is a side view of a drill sleeve of the guide of FIG. 1.

FIG. 3B is an enlarged perspective view of a distal tip of the drill sleeve of FIG. 3A.

FIG. 4 is a side view of a guide arm of the guide of FIG. 1.

FIG. 5 is a side view of the guide of FIG. 1 positioned in a patient's knee.

FIGS. 6-19 are side views of different embodiments of the guide arm.

DETAILED DESCRIPTION

FIG. 1 shows aguide 100 for positioning a tibial tunnel in ACL reconstruction. Briefly,guide 100, which is described in detail below, includes ahandle 105, aguide arm 110 located at oneend 115 ofhandle 105, and a drill sleeve 120 (or "bullet") located at anopposite end 125 ofhandle 105. Adistal tip 130 ofguide arm 110 is configured to contact a femoral surface (e.g., the posterior cortex of the femoral notch), and adistal tip 140 ofdrill sleeve 120 is configured to contact a tibial surface (e.g., the anterior-medial surface of the tibia) when thedistal tip 130 of theguide arm 110 contacts the femoral surface.Drill sleeve 120 is configured to direct a guidewire into the tibial surface to locate the tibial tunnel.

Handle 105 is shown in detail in FIG. 2A. The exterior surface ofhandle 105 is curved so that the surgeon may easily grasp and manipulateguide 100 during surgery. Handle 105 has acylindrical bore 135 atend 125.Bore 135 provides a passageway fordrill sleeve 120. A one-way ratchet 145 is located on one side ofbore 135.Ratchet 145 engagesdrill sleeve 120 and holdsdrill sleeve 120 in place withinbore 135. Handle 105 also has an arc-shapedslot 150 extending fromend 115.Openings 155 in the bottom ofslot 150make handle 105 lightweight.Openings 155 also ensure thathandle 105 cools quickly after autoclaving. As shown in FIG. 2B,slot 150 has a dovetail cross-section.

Handle 105 also has a locking-nut 160 that engagesguide arm 110 and holdsguide arm 110 in place inslot 150. This permits the surgeon to adjust the orientation ofguide arm 110 with respect to drillsleeve 120. For example, when locking-nut 160 is loosened,guide arm 110 is free to slide alongslot 150.

Drill sleeve 120 is sized for insertion throughbore 135. As shown in detail in FIG. 3A,drill sleeve 120 has anelongated body 165, an angleddistal tip 140, and aknob 175 at its proximal end.Body 165 has acylindrical bore 180 that provides a passageway for a guidewire. Markings 170 (e.g., 20 mm, 30 mm, 40 mm) on the exterior ofbody 165 are used to measure the length of the tibial tunnel before drilling the guidewire through the tibia.Drill sleeve 120 also has ratchetteeth 185 along one side ofbody 165. One-way ratchet 145 ofhandle 105 engages ratchetteeth 185 ondrill sleeve 120 and holdsdrill sleeve 120 in place withinbore 135.

Drill sleeve 120 has aknob 175 at its proximal end so that the surgeon may easily grasp and manipulatedrill sleeve 120 during surgery.Knob 175 is larger than thebore 135. Thus, whendrill sleeve 120 is inserted throughbore 135,knob 175 preventsdrill sleeve 120 from being inserted completely throughbore 135.

As shown in detail in FIG. 3B,tip 140 has anangled opening 190 surrounded byteeth 195. Whendrill sleeve 120 is inserted throughbore 135,tip 140 provides a stable engagement betweendrill sleeve 120 and the angled, anterior-medial surface of the tibia. Becauseangled opening 190 oftip 140 is flush against the angled tibial surface,teeth 195 fully contact the bone surface. Moreover,drill sleeve 120 supports the guidewire to the tibial surface to prevent the guidewire from being deflected by the hard bone surface. When the distal tip is not angled, there may be a gap between the teeth and the bone surface, which could result in deflection of the guidewire out of the drill sleeve through the gap.

As shown in detail in FIG. 4,guide arm 110 has aproximal arm portion 200 and adistal arm portion 205.Proximal arm portion 200 is connected to handle 105 atend 115 and extends throughslot 150.Proximal arm portion 200 is sized and shaped to fit inslot 150. For this reason,proximal arm portion 200 is arc-shaped and has a dovetail cross-section. The corresponding dovetail shapes ofproximal arm portion 200 and slot 150 help to keepproximal arm portion 200 withinslot 150.Proximal arm portion 200 also has markings 210 (e.g., 40° , 45° , 50° ) for indicating the orientation ofguide arm 110 with respect to drillsleeve 120.

Distal arm portion 205 has adistal tip 130 with afemoral cortex hook 215 and aspike 220. The size ofspike 220 may vary depending on the desired ease of insertion ofguide arm 110. For example, guidearm 110 is easy to insert into the patient's knee whenspike 220 is short.

The use ofguide 100 will now be described with reference to FIG. 5. As noted above, guide 110 has a femoral offsetguide arm 110. Generally, the femoral offset guide arm references a femoral surface, such as, for example, the posterior cortex of the femoral notch, for positioning the tibial tunnel. Whenguide 100 is positioned in the patient's knee, the femoral offsetguide arm 110 provides an offset 0 from a point at whichhook 215 contacts the femoral surface (e.g., the posterior cortex of the femoral notch) to the longitudinal axis X of drill sleeve 120 (i.e., the axis of the tibial tunnel).

The surgeon adjusts the orientation ofguide arm 110 with respect to drillsleeve 120 by slidingproximal arm portion 200 alongslot 150 ofhandle 105. For example, the orientation ofguide arm 110 with respect to drillsleeve 120 may vary depending on whether the surgeon is using a patellar tendon graft or a semitendinosus tendon graft. Moreover, by adjusting the orientation ofguide arm 110 with respect to drillsleeve 120, the surgeon may vary the length of the tibial tunnel to compensate for the length of the graft.

Markings 210 indicate the orientation ofguide arm 110 with respect to drillsleeve 120.Guide arm 110 is positioned in the desired orientation by tightening locking-nut 160.Hook 215 atdistal tip 130 ofguide arm 110 is positioned against the posterior cortex of the femoral notch, and spike 220 is embedded in the anterior portion of the tibial plateau to holdguide arm 110 in place.Guide arm 110 is sized and shaped to provide an offset 0 from a point at whichhook 215 contacts the femoral surface (e.g, the posterior cortex of the femoral notch) to the longitudinal axis X of drill sleeve 120 (i.e., the axis of the tibial tunnel).

Drill sleeve 120 is inserted throughbore 135 ofhandle 105 so thatangled opening 190 is flush against the angled, anterior-medial surface of the tibia, andteeth 195 fully contact the bone surface.Drill sleeve 120 is maintained within thebore 135 by one-way ratchet 145. Becausedrill sleeve 120 has ratchetteeth 185 along only one side ofbody 165,drill sleeve 120 may be adjusted withinbore 135 by turningdrill sleeve 120 such that ratchetteeth 185 no longer engage one-way ratchet 145.

Markings 170 are used to indicate the length of the tibial tunnel before drilling the guidewire. In particular,markings 170 measure the distance fromangled opening 190 ofdrill sleeve 120 to a point at which the longitudinal axis X ofdrill sleeve 120 intersects the tibial plateau.

A guidewire (not shown) is inserted throughdrill sleeve 120 and drilled through the tibia. Becauseangled opening 190 is flush against the angled tibial surface,drill sleeve 120 supports the guidewire to the tibial surface to prevent the guidewire from being deflected by the hard bone surface.Guide 100 is then removed from the patient's knee, leaving the guidewire in place. Finally, a cannulated drill bit is placed over the guidewire for drilling the tibial tunnel.

FIGS. 6-19 show other embodiments of a femoral offset guide arm. In the embodiment shown in FIG. 6,guide arm 300 has ahook 305 and aspike 310.Spike 310 is long and thus, easy for the surgeon to see in the patient's knee.Spike 310 also may indicate where the guidewire will emerge from the tibial plateau, i.e., the location of the tibial tunnel opening.

In the embodiment shown in FIG. 7,guide arm 320 has ahook 325, but no spike. Becauseguide arm 320 does not have a spike,guide arm 320 is easy to insert into the patient's knee, but must be held in place by the surgeon.

FIGS. 8-12 show other embodiments of the femoral offset guide arm (400a-400e), each of which has two distal arm portions: a distal spike arm portion (405a-405e)and a distal hook arm portion (410a-410e). Distal spike arm portion (405a-405e)has a spike (415a-415e)at its distal tip, and distal hook arm portion (410a-410e)has a femoral cortex hook (420a-420e)at its distal tip.

In FIG. 8,spike arm portion 405a is inserted into the patient's knee, andspike 415a is embedded into the tibial plateau.Hook 420a is then positioned against the posterior cortex of the femoral notch by sliding distalhook arm portion 410a over distalspike arm portion 405a. The position of distalhook arm portion 410a with respect to distalspike arm portion 405a may be adjusted bycam 425.Cam 425 also holds the distalhook arm portion 410a in place. Thus, guidearm 400a may be adjusted to compensate for various femoral offsets.Guide arm 400a is easy to insert into the patient's knee because distalhook arm portion 410a is not in place when distalspike arm portion 405a is inserted. If desired, however, the surgeon may insert distalspike arm portion 405a and distalhook arm portion 410a together into the patient's knee.

In FIG. 9,spike arm portion 405b is inserted into the patient's knee, andspike 415b is embedded into the tibial plateau.Hook 420b is positioned against the posterior cortex of the femoral notch by sliding distalhook arm portion 410b over distalspike arm portion 405b. Distalhook arm portion 410b is then connected to distalspike arm portion 405b at pivot point A. For example, distalhook arm portion 410b may be connected to distalspike arm portion 405b by use of male/female connectors or a pin. Aspring 435 attached to the bottom of distalhook arm portion 410b pushes distalhook arm portion 410b against the femoral notch. Thus, guidearm 400b is adjusted to compensate for various femoral notch heights.Guide arm 400b is easy to insert into the patient's knee because distalhook arm portion 410b is not in place when distalspike arm portion 405b is inserted. If desired, however, the surgeon may insert distalspike arm portion 405b and distalhook arm portion 410b together into the patient's knee.

Referring to FIG. 10,guide arm 400c may be adjusted to compensate for various femoral notch heights.Spike arm portion 405c is inserted into the patient's knee, andspike 415c is embedded into the tibial plateau.Hook 420c is then positioned against the posterior cortex of the femoral notch by sliding distalhook arm portion 410c over distalspike arm portion 405c. Aspring 440 attached to distalhook arm portion 410c and distalspike arm portion 405c pushes distalhook arm portion 410c against the femoral notch.Guide arm 400c is easy to insert into the patient's knee because distalhook arm portion 410c is not in place when distalspike arm portion 405c is inserted. If desired, however, the surgeon may insert distalspike arm portion 405c and distalhook arm portion 410c together into the patient's knee.

FIG. 11 shows another embodiment of a femoral offset guide arm that can be adjusted to compensate for various femoral notch heights. Distalhook arm portion 410d is attached to distalspike arm portion 405d by fourbar linkages 445, 450, which are mounted in pairs on opposite sides of the guide arm.Linkages 445, 450 are attached to distalhook arm portion 410d at pivot points B and to distalspike arm portion 405d at pivot pointsC. Guide arm 400d is easy to insert into the patient's knee because distalhook arm portion 410d is not in place when distalspike arm portion 405d is inserted. If desired, however, the surgeon may insert distalspike arm portion 405d and distalhook arm portion 410d together into the patient's knee.

In FIG. 12, distalspike arm portion 405e is attached to distalhook arm portion 410e at two pivot points D and E. This permits alignment ofspike 415e withhook 420e during insertion, so thatguide arm 400e is easy to insert into the patient's knee. Afterhook 420e is positioned against the posterior cortex of the femoral notch, distalspike arm portion 405e is lowered, thereby embeddingspike 415e in the tibial plateau.

FIGS. 13-17 show embodiments of a femoral offset guide arm that can also be used to determine isometry. Isometry exists when the distance between the femoral tunnel opening F and tibial tunnel opening T remains constant during extension of the knee. In other words, the length of the graft remains constant during extension of the knee. Referring to FIG. 13,guide arm 500 has afemoral cortex hook 505 attached to aspike 510 by anisometry linkage 515.Isometry linkage 515 is movably attached to spike 510 and pivots around the tibial tunnel opening T. Whenhook 505 is positioned against the posterior cortex of the femoral notch,guide arm 500 may be adjusted by pivotingisometry linkage 515 around T. Isometry exists whenspike 510 does not move during extension of the knee.Isometry linkage 515 is available in different lengths because the height of the femoral notch varies from patient to patient.

In FIG. 14,guide arm 520 has afemoral cortex hook 525 attached to aspike 530 by anadjustable isometry linkage 535. The length ofisometry linkage 535 is controlled throughhydraulic means 540. In this embodiment, isometry exists when the length ofisometry linkage 535 remains constant during extension of the knee.

In FIG. 15,guide arm 550 has two distal arm portions: a distalspike arm portion 555 and a distalhook arm portion 560. Distalspike arm portion 555 has aspike 565 at its distal tip, and distalhook arm portion 560 has afemoral cortex hook 570 at its distal tip. Anisometry mechanism 575 is connected to distalspike arm portion 555 and distalhook arm portion 560 and indicates any change in distance betweenhook 570 and spike 565 during extension of the knee. This isometry mechanism may be located outside the patient's knee. For example,isometry mechanism 575 could be a spring attached to a scale for measuring any change in distance betweenhook 570 and spike 565. Isometry exists when there is no change in distance betweenhook 570 and spike 565 during extension of the knee.

In the embodiment shown in FIG. 16,guide arm 600 has adistal tip 605 with afemoral cortex hook 610 attached to aspike 615 at pivot point G. A stop 620 limits the pivoting action ofhook 610. Stop 620 also may include a spring (not shown) to pushhook 610 against the femoral notch. The effective length ofdistal tip 605 may be adjusted by pivotingguide arm 600 aroundspike 615, thereby moving pivot point G either up or down. Isometry exists when pivot point G does not move during extension of the knee.

In FIG. 17,guide arm 630 has two distal arm portions: a distalspike arm portion 635 and a distalhook arm portion 640. Distalspike arm portion 635 has aspike 645 at its distal tip, and distalhook arm portion 640 has afemoral cortex hook 650 at its distal tip.Isometry suture 655 is connected to spike 645 and hook 650 using apulley mechanism 660.Isometry suture 655 indicates any change in distance between thespike 645 andhook 650 during extension of the knee. Isometry exists when there is no suture movement.

FIG. 18 shows another embodiment of a femoral offset guide arm.Guide arm 700 references the femur for positioning the tibial and femoral tunnels. In this embodiment,guide arm 700 has adistal tip 705 with afemoral cortex hook 710, aspike 715, and an S-shapedslot 720 for insertion of a guidewire. When the guidewire is drilled through the tibia, the guidewire exits the tibia at T, extends throughslot 720, and enters the femur at F. Thus, slot 720 redirects the guidewire from the tibial tunnel opening T to the femoral tunnel openingF. Slot 720 extends to one side ofdistal tip 705 so thatguide arm 700 may be removed from the patient's knee, leaving the guidewire in place. The guidewire locates the positions of the tibial and femoral tunnels.

FIG. 19 shows another embodiment of a femoral offset guide arm. Generally, the femoral tunnel is positioned as posterior as possible on the femoral notch.Guide arm 800 references the posterior region of the femoral notch (e.g., the desired site of femoral tunnel opening) for positioning the tibial tunnel.Guide arm 800 provides an offset 0 from the reference point (e.g., the desired site of femoral tunnel opening) to the longitudinal axis X of drill sleeve 10 (i.e., the axis of the tibial tunnel).Guide arm 800 also measures the interarticular joint space or ACL length. Thus, the surgeon may adjust the length of the tibial tunnel to compensate for the length of the graft.

As shown in FIG. 19,guide arm 800 has a passageway for awire 805 made from Nitinol or other high strain recovery material.Wire 805 is attached to aswitch 810 and extends through or alongguide arm 800 and out ofdistal tip 815. Aspike 820 is embedded in the tibial plateau. In use,wire 805 is advanced out ofdistal tip 815 untilwire 805 contacts the posterior region of the femoral notch at the desired site of the femoral tunnel opening.Markings 825 also indicate howmuch wire 805 has advanced out ofdistal tip 815 and thus, the length of the ACL. In another embodiment, a laser may be used to point to the femoral tunnel opening.

In yet another embodiment, a femoral offset guide arm may be used with an "acorn" reamer. An acorn reamer is a reamer having a shank that is smaller than its head. After drilling the tibial tunnel, the surgeon often uses an acorn reamer to form the femoral tunnel in the posterior region of the femoral notch. In this embodiment, the guide arm positions the tibial tunnel to ensure that the acorn reamer reaches the posterior region of the femoral notch.

The femoral offset guide arm also may be used to avoid impingement. Impingement occurs when the graft hits the femoral notch during extension of the knee. To avoid impingement, a three-dimensional representation of the graft is attached to the distal tip of the guide arm so that the surgeon can determine whether the graft will hit the femoral notch during extension of the knee.

There has been described novel and improved apparatus and techniques for positioning a tibial tunnel in ACL reconstruction. It is evident that those skilled in the art may now make numerous uses and modifications of and departures from the specific embodiments described herein without departing from the inventive concept.

Claims (25)

What is claimed is:

1. A guide for positioning a tibial tunnel, the guide comprising:

a guide arm having a rigid distal tip configured to contact a femoral surface; and

a drill sleeve connected to the guide arm and having a distal tip configured to contact a tibial surface when the distal tip of the guide arm contacts the femoral surface.

2. The guide in claim 1 further comprising a handle, wherein the guide arm is connected to the handle, and the drill sleeve is connected to the handle, and wherein the guide arm and drill sleeve are connected through their connections to the handle.

3. The guide in claim 2 wherein the guide arm is located at one end of the handle, and the drill sleeve is located at an opposite end of the handle.

4. The guide in claim 1 wherein an orientation of the guide arm may be adjusted with respect to the drill sleeve.

5. The guide in claim 4 wherein the guide arm has markings for indicating the orientation of the guide arm with respect to the drill sleeve.

6. The guide in claim 1 wherein the drill sleeve is configured to direct a guidewire into the tibial surface to locate the tibial tunnel.

7. The guide in claim 1 wherein the drill sleeve has markings for measuring the length of the tibial tunnel.

8. The guide in claim 1 wherein the distal tip of the drill sleeve comprises an angled opening surrounded by teeth.

9. The guide in claim 1 wherein the distal tip of the guide arm comprises a hook configured to contact the femoral surface.

10. The guide in claim 9 wherein the distal tip of the guide arm further comprises a spike configured to contact a tibial plateau.

11. The guide in claim 1 wherein the distal tip of the guide arm is configured to contact the posterior cortex of the femoral notch.

12. The guide in claim 1 wherein the guide arm is configured to provide an offset from a point at which the distal tip contacts the femoral surface to a longitudinal axis of the drill sleeve.

13. The guide in claim 1 wherein the guide arm comprises a first distal arm portion having a hook configured to contact the femoral surface and a second distal arm portion having a spike configured to contact a tibial plateau.

14. The guide in claim 13 wherein the first distal arm portion arm is configured to slide over the second distal arm portion.

15. The guide in claim 13 wherein the first distal arm portion is attached to the second distal arm portion by a spring.

16. The guide in claim 13 wherein the first distal arm portion is attached to the second distal arm portion by a linkage.

17. The guide in claim 13 wherein the first distal arm portion is attached to the second distal arm portion at a pivot point.

18. The guide in claim 1 further comprising a device for indicating isometry.

19. The guide in claim 18 wherein the device comprises an isometry linkage.

20. The guide in claim 19 further comprising means for extending the isometry linkage.

21. The guide in claim 20 wherein the extending means comprises hydraulic means.

22. The guide in claim 18 wherein the device comprises an isometry mechanism.

23. The guide in claim 22 wherein the isometry mechanism comprises a spring.

24. The guide in claim 18 wherein the device comprises an isometry suture.

25. A drill sleeve comprising a distal tip having an angled opening surrounded by teeth, wherein the angled opening defines a plane that forms an oblique angle with a longitudinal axis of the drill sleeve.

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